1. Field of the Invention
This invention relates to a position detecting system in which a predetermined pattern in an image is searched for and its position is detected.
2. Description of the Prior Art
As a system wherein a certain specific pattern is distinguished from other patterns and a background pattern and sampled from within a two-dimensional image picked up by an imaging device, such as television camera, and its position in the two-dimensional image is evaluated, there has heretofore been known one wherein local patterns of an object are stored as standard patterns, the standard patterns and segmented patterns of predetermined size at various positions in the image inputted by the imaging device are sequentially compared with each other, and the best coincident coordinate position is detected, thereby to detect the position of the whole object.
In this case, the segmented pattern is sampled at a fixed sampling interval corresponding to the interval of sampling points of the standard pattern, and it is compared with the standard pattern.
Accordingly, the pattern detecting accuracy is determined by the sampling interval. When the sampling interval is therefore made small in order to enhance the detection accuracy more, a smaller pattern need be used as the standard pattern. It occurs that such standard pattern cannot become a pattern having a feature, and it substantially becomes difficult to detect the position of the specific pattern.
In short, the prior-art system described above has the disadvantage that the detection accuracy is determined by the size of the local standard pattern having the feature on the object and that it becomes extremely poor in some cases.